The present invention relates, in general, to wireless communication systems, and more particularly, to an apparatus, method and system for mobile wireless communication hand-off utilizing shared directory numbers.
Mobile wireless communication systems typically employ many base stations (such as cell sites) to provide wireless communication throughout a given geographic region. As a mobile unit (or, equivalently, mobile station) may traverse the geographic region, the communication to and from the mobile unit may occur through one or more of these base stations. To maintain an ongoing communication session during such transitions between base stations, various hand-off methods have evolved to transfer the wireless communication with the mobile unit from one base station to another base station, while maintaining such an ongoing call or session.
In the prior art, for some of the various methods utilized during such hand-offs, the communication session may suffer from some degree of interruption, which may be noticeable to the consumer of wireless communication services. As a consequence, a need remains to provide for comparatively seamless hand-offs, which do not interrupt ongoing communication sessions and which are imperceptible to the consumer.
In addition, while other prior art systems may provide comparatively seamless hand-offs, such hand-offs typically utilize considerable network resources. In an Autoplex(copyright) system, for example, in addition to switches and base stations, another network entity referred to as an Executive Call Processor (xe2x80x9cECPxe2x80x9d) selects a server at the new cell site, while another network entity referred to as a Call Processing Database Node (xe2x80x9cCDNxe2x80x9d) transmits various data link messages to the current and new cell sites, adding an additional path to the existing call, directing the new cell site to activate a wireless voice link, and directing the current (serving) cell site to direct the mobile to retune to the new wireless voice link at the new cell site.
As a consequence, a need remains for a wireless communication system to provide comparatively seamless and imperceptible hand-offs. In addition, such a wireless communication system should be reasonably efficient and capable of cost-effective implementation, eliminating or minimizing the use of additional network resources.
The wireless communication system of the present invention provides virtually seamless and imperceptible hand-offs of communication sessions of mobile units. The various embodiments of the present invention are reasonably efficient and capable of cost-effective implementation in existing communication equipment such as switches and base stations. Moreover, the various embodiments of the present invention eliminate or minimize the use of additional network resources such as ECPs and CDNs, while being compatible with other intelligent network devices and systems.
In accordance with the present invention, an apparatus, method and system are provided for hand-off of a communication session utilizing shared directory numbers, in which the communication session of a mobile unit is transferred from a serving base station to a target base station. The preferred system includes a switch coupled to a serving base station and a target base station. Typically, each of the various base stations include a plurality of terminals which handle and process the communication sessions with mobile units and, in general, one or more terminals are assigned directory numbers (xe2x80x9cDNsxe2x80x9d). In accordance with the present invention, such DNs are shared by terminals in both the serving and target base stations.
When a hand-off of the communication session is indicated, the serving base station transmits a message, to the target base station, designating the shared directory number of the (first) terminal within the serving base station which is currently handling the communication session to be handed-off. The target base station then transmits a request or other message to the switch to join or bridge into the communication session at the specified or designated shared directory number. The switch then creates a bridged call path from the target base station (using a (second) terminal within the target base station having the same (i.e., shared) designated DN (of the first terminal within the serving base station), to the communication session of the first terminal within serving base station, to form a (reverse) three-way communication session among the mobile unit (via the serving base station), the target base station, and the switch. The mobile unit is then directed to communicate with the target base station for continuation of the communication session through the bridged call path, and the switch releases the serving base station from the three-way communication session.
As a consequence, the communication session of the mobile unit has been handed off, seamlessly and without interruption, from the serving base station to the target base station. Such a hand-off has also occurred utilizing minimal network resources, the switch and the base stations, without involvement of other intelligent or supervisory network elements.
The bridged call path from the target base station to the switch is established through the transmission of various messages between the target base station and the switch. The switch is correspondingly configured to acknowledge and connect the bridged call path to the communication session upon receipt of these various messages. In the various embodiments, depending upon the ISDN configuration, such as custom or national, the target base station is configured to transmit a xe2x80x9cRECONNECTxe2x80x9d or xe2x80x9cRETRIEVExe2x80x9d message, with the switch configured to transmit corresponding acknowledgements and other messages.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.